Modified zeolites that include hafnium-containing organometallic moieties and methods for making such

ABSTRACT

Disclosed herein are modified zeolites and methods for making modified zeolites. In one or more embodiments disclosed herein, a modified zeolite may include a microporous framework including a plurality of micropores having diameters of less than or equal to 2 nm. The microporous framework includes at least silicon atoms and oxygen atoms. The modified zeolite may further include organometallic moieties each bonded to bridging oxygen atoms. The organometallic moieties include a hafnium atom. The hafnium atom is bonded to a bridging oxygen atom, and bridging oxygen atom bridges the hafnium atom of the organometallic moiety and a silicon atom of the microporous framework.

TECHNICAL FIELD

The present disclosure generally relates to porous materials and, morespecifically, to zeolites.

BACKGROUND

Materials that include pores, such as zeolites, may be utilized in manypetrochemical industrial applications. For example, such materials maybe utilized as catalysts in a number of reactions which converthydrocarbons or other reactants from feed chemicals to productchemicals. Zeolites may be characterized by a microporous structureframework type. Various types of zeolites have been identified over thepast several decades, where zeolite types are generally described byframework types, and where specific zeolitic materials may be morespecifically identified by various names such as ZSM-5 or Beta.

BRIEF SUMMARY

The present application is directed to modified zeolites that includeorganometallic moieties. The organometallic moieties described hereinmay include hafnium. According to various embodiments, theorganometallic moieties may be grafted to isolated terminal silanolfunctionalities of a precursor zeolite, referred to sometimes herein asdehydroxylated zeolites. As such, the modified zeolites described hereinmay include organometallic moieties whereby the hafnium atom of theorganometallic moiety is bonded to an oxygen atom that bridges thehafnium atom and a silicon atom of the microporous framework of themodified zeolite. Such modified zeolites, according to one or moreembodiments presently disclosed, may have enhanced or differentiatedcatalytic functionality as compared with conventional zeolites.

In accordance with one or more embodiments of the present disclosure, amodified zeolite may comprise a microporous framework comprising aplurality of micropores having diameters of less than or equal to 2 nm.The microporous framework may comprise at least silicon atoms and oxygenatoms. The modified zeolite may further comprise organometallic moietieseach bonded to bridging oxygen atoms. The organometallic moieties maycomprise a hafnium atom. The hafnium atom may be bonded to a bridgingoxygen atom, and bridging oxygen atom may bridge the hafnium atom of theorganometallic moiety and a silicon atom of the microporous framework.

In accordance with one or more additional embodiments of the presentdisclosure, a modified zeolite may be made by a method comprisingreacting an organometallic chemical with a dehydroxylated zeolite. Thedehydroxylated zeolite may comprise a microporous framework comprising aplurality of micropores having diameters of less than or equal to 2 nm.The microporous framework may comprise at least silicon atoms and oxygenatoms. The dehydroxylated zeolite may comprise terminal isolated silanolfunctionalities comprising hydroxyl groups bonded to silicon atoms ofthe microporous framework. The reacting of the organometallic chemicalwith the dehydroxylated zeolite may form the modified zeolite includingorganometallic moieties each bonded to an oxygen atom of the modifiedzeolite. The organometallic moiety may comprise a portion of theorganometallic chemical, and the organometallic chemical may comprisehafnium.

Additional features and advantages of the described embodiments will beset forth in the detailed description which follows, and in part will bereadily apparent to those skilled in the art from that description orrecognized by practicing the described embodiments, including thedetailed description which follows, the claims, as well as the appendeddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of specific embodiments of thepresent disclosure can be best understood when read in conjunction withthe following drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 depicts a reaction pathway to formpoly(N¹,N¹-diallyl-N-methyl-N⁶,N⁶,N⁶-tripropylhexane-1,6-diamoniumbromide) (PDAMAB-TMHAB), according to one or more embodiments describedin this disclosure;

FIG. 2 depicts a Proton Nuclear Magnetic Resonance (¹H-NMR) spectrum ofPDAMAB-TMHAB as synthesized in Example 1, according to one or moreembodiments described in this disclosure;

FIG. 3 depicts a Powder X-Ray Diffraction (PXRD) pattern of themesoporous ZSM-5 zeolite of Example 2, according to one or moreembodiments described in this disclosure;

FIGS. 4A and 4B depict Scanning Electron Microscope (SEM) images of themesoporous ZSM-5 zeolite of Example 2, according to one or moreembodiments described in this disclosure;

FIG. 5A-5K depict Transmission Electron Microscope (TEM) images of themesoporous ZSM-5 zeolite of Example 2, according to one or moreembodiments described in this disclosure;

FIG. 6 depicts Fourier Transform Infrared (FT-IR) spectra of themesoporous ZSM-5 zeolite of Example 2 and the dehydroxylated ZSM-5zeolite of Example 3, according to one or more embodiments described inthis disclosure;

FIG. 7 depicts a ¹H-MAS-NMR spectrum of the dehydroxylated ZSM-5 zeoliteof Example 3 according to one or more embodiments described in thisdisclosure;

FIG. 8 depicts an Aluminum Solid State Nuclear Magnetic Resonance(²⁷Al—SS-NMR) spectrum of the dehydroxylated ZSM-5 zeolite of Example 3according to one or more embodiments described in this disclosure; and

FIG. 9 depicts FT-IR spectra of the dehydroxylated ZSM-5 zeolite ofExample 3 and the hafnium modified ZSM-5 zeolite of Example 4, accordingto one or more embodiments described in this disclosure.

Reference will now be made in greater detail to various embodiments,some embodiments of which are illustrated in the accompanying drawings.Whenever possible, the same reference numerals will be used throughoutthe drawings to refer to the same or similar parts.

DETAILED DESCRIPTION

The present disclosure is directed to zeolites which are modified by thegrafting of organometallic moieties to the framework structure of thezeolite. As presently described, the organometallic moieties may includehafnium. As referred to herein, “modified zeolites” refer to zeoliteswhich include organometallic moieties as described herein. According toone or more of the embodiments disclosed herein, the modified zeolitemay include an organometallic each bonded to bridging oxygen atoms. Thebridging oxygen atom may bridge the hafnium atom of the organometallicmoiety and a silicon atom of the microporous framework of the modifiedzeolite.

According to embodiments disclosed herein, the modified zeolites may beformed by a process that includes dehydroxylating an initial zeolite,and grafting organometallic chemicals to the dehydroxylated zeolite.While embodiments of modified zeolites prepared by this procedure aredisclosed herein, embodiments of the present disclosure should not beconsidered to be limited to modified zeolites made by such a process.

As presently described, “initial” zeolites (which in some embodimentsmay be mesoporous zeolites) may be supplied or produced, as is presentlydisclosed. Initial zeolites may include mesopores or be void ofmesopores. In embodiments where mesopores are introduced to a zeolite in“top-down” approach, the zeolite with the formed mesopores may beconsidered the initial zeolite. As described herein, thecharacterization of the structure and material of the zeolite mayequally apply to the initial zeolite as well as the dehydroxylatedzeolite and/or modified zeolite. In one or more embodiments, thestructure and material composition of the initial zeolite does notsubstantially change through the dehydroxylation steps and/ororganometallic grafting steps (aside from the introduction of thedescribed functionalities formed by the dehydroxylation and/ororganometallic moiety grafting steps). For example, the framework typeand general material constituents of the framework may be substantiallythe same in the initial zeolite and the modified zeolite aside from theaddition of the organometallic moiety. Likewise, mesoporosity of theinitial zeolite may be carried into the modified zeolite. Accordingly,when a “zeolite” is described herein with respect to its structuralcharacterization, the description may refer to the initial zeolite, thedehydroxylated zeolite, and/or the modified zeolite.

As used throughout this disclosure, “zeolites” may refer tomicropore-containing inorganic materials with regular intra-crystallinecavities and channels of molecular dimension. Zeolites generallycomprise a crystalline structure, as opposed to an amorphous structuresuch as what may be observed in some porous materials such as amorphoussilica. Zeolites generally include a microporous framework which may beidentified by a framework type. The microporous structure of zeolites(e.g., 0.3 nm to 2 nm pore size) may render large surface areas anddesirable size-/shape-selectivity, which may be advantageous forcatalysis. The zeolites described may include, for example,aluminosilicates, titanosilicates, or pure silicates. In embodiments,the zeolites described may include micropores (present in themicrostructure of a zeolite), and additionally include mesopores. Asused throughout this disclosure, micropores refer to pores in astructure that have a diameter of less than or equal to 2 nm and greaterthan or equal to 0.1 nm, and mesopores refer to pores in a structurethat have a diameter of greater than 2 nm and less than or equal to 50nm. Unless otherwise described herein, the “pore size” of a materialrefers to the average pore size, but materials may additionally includemesopores having a particular size that is not identical to the averagepore size.

Generally, zeolites may be characterized by a framework type whichdefines their microporous structure. The zeolites described presently,in one or more embodiments, are not particularly limited by frameworktype. Framework types are described in, for example, “Atlas of ZeoliteFramework Types” by Ch. Baerlocher et al, Fifth Revised Edition, 2001,which is incorporated by reference herein.

According to one or more embodiments, the zeolites described herein mayinclude at least silicon atoms and oxygen atoms. In some embodiments,the microporous framework may include substantially only silicon andoxygen atoms (e.g., silica material). However, in additionalembodiments, the zeolites may include other atoms, such as aluminum.Such zeolites may be aluminosilicate zeolites. In additionalembodiments, the microporous framework may include titanium atoms, andsuch zeolites may be titanosilicate zeolites.

In one or more embodiments, the zeolite may comprise an aluminosilicatemicrostructure. The zeolite may comprise at least 99 wt. % of thecombination of silicon atoms, oxygen atoms, and aluminum atoms. Themolar ratio of Si/Al may be from 2 to 100, such as from 2-25, from25-50, from 50-75, from 75-100, or any combination of these ranges.

In embodiments, the zeolites may comprise microstructures (which includemicropores) characterized by, among others as *BEA framework typezeolites (such as, but not limited to, zeolite Beta), FAU framework typezeolites (such as, but not limited to, zeolite Y), MOR framework typezeolites, or MFI framework type zeolites (such as, but not limited to,ZSM-5). It should be understood that *BEA, MFI, MOR, and FAU refer tozeolite framework types as identified by their respective three lettercodes established by the International Zeolite Association (IZA). Otherframework types are contemplated in the presently disclosed embodiments.

In one or more embodiments, the zeolite may be an MFI framework typezeolite, such as a ZSM-5. “ZSM-5” generally refers to zeolites having anMFI framework type according to the IZA zeolite nomenclature andconsisting majorly of silica and alumina, as is understood by thoseskilled in the art. ZSM-5 refers to “Zeolite Socony Mobil-5” and is apentasil family zeolite that can be represented by the chemical formulaNa_(n)Al_(n)Si₉₆-nO₁₉₆.16H₂O, where 0<n<27. According to one or moreembodiments, the molar ratio of silica to alumina in the ZSM-5 may be atleast 5. For example, the molar ratio of silica to alumina in the ZSM-5zeolite may be at least 10, at least 12, or even at least 30, such asfrom 5 to 30, from 12 to 30, from 5 to 80, from 5 to 300, from 5 to1000, or even from 5 to 1500. Examples of suitable ZSM-5 zeolite includethose commercially available from Zeolyst International, such asCBV2314, CBV3024E, CBV5524G, and CBV28014, and from TOSOH Corporation,such as HSZ-890 and HSZ-891.

In one or more embodiments, the zeolite may comprise an FAU frameworktype zeolite, such as zeolite Y or ultra-stable zeolite Y (USY). As usedherein, “zeolite Y” and “USY” refer to a zeolite having a FAU frameworktype according to the IZA zeolite nomenclature and consisting majorly ofsilica and alumina, as would be understood by one skilled in the art. Inone or more embodiments, USY may be prepared from zeolite Y by steamingzeolite Y at temperatures above 500° C. The molar ratio of silica toalumina may be at least 3. For example, the molar ratio of silica toalumina in the zeolite Y may be at least 5, at least 12, at least 30, oreven at least 200, such as from 5 to 200, from 12 to 200, or from about15 to about 200. The unit cell size of the zeolite Y may be from about24 Angstrom to about 25 Angstrom, such as 24.56 Angstrom.

In one or more embodiments, the zeolite may comprise a *BEA frameworktype zeolite, such as zeolite Beta. As used in this disclosure, “zeoliteBeta” refers to zeolite having a *BEA framework type according to theIZA zeolite nomenclature and consisting majorly of silica and alumina,as would be understood by one skilled in the art. The molar ratio ofsilica to alumina in the zeolite Beta may be at least 10, at least 25,or even at least 100. For example, the molar ratio of silica to aluminain the zeolite Beta may be from 5 to 500, such as from 25 to 300.

Along with micropores, which may generally define the framework type ofthe zeolite, the zeolites may also comprise mesopores. As used herein a“mesoporous zeolite” refers to a zeolite which includes mesopores, andmay have an average pore size of from 2 to 50 nm. The presentlydisclosed mesoporous zeolites may have an average pore size of greaterthan 2 nm, such as from 4 nm to 16 nm, from 6 nm to 14 nm, from 8 nm to12 nm, or from 9 nm to 11 nm. In some embodiments, the majority of themesopores may be greater than 8 nm, greater than 9 nm, or even greaterthan 10 nm. The mesopores of the mesoporous zeolites described may rangefrom 2 nm to 40 nm, and the median pore size may be from 8 to 12 nm. Inembodiments, the mesopore structure of the zeolites may be fibrous,where the mesopores are channel-like. As described herein, “fibrouszeolites” may comprise reticulate fibers with interconnections and havea dense inner core surrounded by less dense outer fibers. Generally,fibrous zeolites may comprise intercrystalline voids in between thefibers where the voids between the less dense, outer fibers are mesoporesized and give the fibrous zeolite its mesoporosity. The mesoporouszeolites described may be generally silica-containing materials, such asaluminosilicates, pure silicates, or titanosilicates. It should beunderstood that while mesoporous zeolites are referenced in one or moreportions of the present disclosure, some zeolites may not be mesoporous.For example, some embodiments may utilize zeolites which have an averagepore size of less than 2 nm, or may not have mesopores in any capacity.

The mesoporous zeolites described in the present disclosure may haveenhanced catalytic activity as compared to non-mesoporous zeolites.Without being bound by theory, it is believed that the microporousstructures provide for the majority of the catalytic functionality ofthe mesoporous zeolites described. The mesoporosity may additionallyallow for greater catalytic functionality because more micropores areavailable for contact with the reactant in a catalytic reaction. Themesopores generally allow for better access to microporous catalyticsites on the mesoporous zeolite, especially when reactant molecules arerelatively large. For example, larger molecules may be able to diffuseinto the mesopores to contact additional catalytic microporous sites.

Additionally, mesoporosity may allow for additional grafting sites onthe zeolite where organometallic moieties may be bound. As is describedherein, organometallic chemicals may be grafted to the microstructure ofthe zeolite. Mesoporosity may allow for additional grafting sites,allowing for greater amounts of organometallic functionalities ascompared with non-mesoporous zeolites.

In embodiments, the mesoporous zeolites may have a surface area ofgreater than or equal to 300 m²/g, greater than or equal to 350 m²/g,greater than or equal to 400 m²/g, greater than or equal to 450 m²/g,greater than or equal to 500 m²/g, greater than or equal to 550 m²/g,greater than or equal to 600 m²/g, greater than or equal to 650 m²/g, oreven greater than or equal to 700 m²/g, and less than or equal to 1,000m²/g. In one or more other embodiments, the mesoporous zeolites may havepore volume of greater than or equal to 0.2 cm³/g, greater than or equalto 0.25 cm³/g, greater than or equal to 0.3 cm³/g, greater than or equalto 0.35 cm³/g, greater than or equal to 0.4 cm³/g, greater than or equalto 0.45 cm³/g, greater than or equal to 0.5 cm³/g, greater than or equalto 0.55 cm³/g, greater than or equal to 0.6 cm³/g, greater than or equalto 0.65 cm³/g, or even greater than or equal to 0.7 cm³/g, and less thanor equal to 1.5 cm³/g. In further embodiments, the portion of thesurface area contributed by mesopores may be greater than or equal to20%, greater than or equal to 25%, greater than or equal to 30%, greaterthan or equal to 35%, greater than or equal to 40%, greater than orequal to 45%, greater than or equal to 50%, greater than or equal to55%, greater than or equal to 60%, or even greater than or equal to 65%,such as between 20% and 70% of total surface area. In additionalembodiments, the portion of the pore volume contributed by mesopores maybe greater than or equal to 20%, greater than or equal to 30%, greaterthan or equal to 35%, greater than or equal to 40%, greater than orequal to 45%, greater than or equal to 50%, greater than or equal to55%, greater than or equal to 60%, greater than or equal to 65%, greaterthan or equal to 70%, or even greater than or equal to 75%, such asbetween 20% and 80% of total pore volume. Surface area, average poresize, and pore volume distribution may be measured by N₂ adsorptionisotherms performed at 77 Kelvin (K) (such as with a Micrometrics ASAP2020 system). As would be understood by those skilled in the artBrunauer-Emmett-Teller (BET) analysis methods may be utilized.

The mesoporous zeolites described may form as particles that may begenerally spherical in shape or irregular globular shaped (that is,non-spherical). In embodiments, the particles have a “particle size”measured as the greatest distance between two points located on a singlezeolite particle. For example, the particle size of a spherical particlewould be its diameter. In other shapes, the particle size is measured asthe distance between the two most distant points of the same particlewhen viewed in a microscope, where these points may lie on outersurfaces of the particle. The particles may have a particle size from 25nm to 900 nm, from 25 nm to 800 nm, from 25 nm to 700 nm, from 25 nm to600 nm, from 25 nm to 500 nm, from 50 nm to 400 nm, from 100 nm to 300nm, or less than 900 nm, less than 800 nm, less than 700 nm, less than600 nm, less than 500 nm, less than 400 nm, less than 300 nm, or lessthan 250 nm. Particle sizes may be determined by visual examinationunder a microscope.

The mesoporous zeolites described may be formed in a single-crystalstructure, or if not single crystal, may consist of a limited number ofcrystals, such as 2, 3, 4, or 5. The crystalline structure of themesoporous zeolites may have a branched, fibrous structure with highlyinterconnected intra-crystalline mesopores. Such structures may beadvantageous in applications where the structural integrity of thezeolite is important while the ordering of the mesopores is not.

According to one or more embodiments, the mesoporous zeolites describedin the present disclosure may be produced by utilizing cationicpolymers, as is subsequently described in the present disclosure, asstructure-directing agents. The cationic polymers may function asdual-function templates for synthesizing the mesoporous zeolites,meaning that they act simultaneously as a template for the fabricationof the micropores and as a template for the fabrication of themesopores.

According to various embodiments, the mesoporous zeolites described inthe present disclosure may be produced by forming a mixture comprisingthe cationic polymer structure-directing agent (SDA), such asPDAMAB-TPHAB, and one or more precursor materials which will form thestructure of the mesoporous zeolites. The precursor materials maycontain the materials that form the porous structures, such as aluminaand silica for an aluminosilicate zeolite, titania and silica for atitanosilicate zeolite, and silica for a pure silica zeolite. Forexample, the precursor materials may be one or more of asilicon-containing material, a titanium-containing material, and analuminum-containing material. For example, at least NaAlO₂, tetra ethylorthosilicate, and the cationic polymer may be mixed in an aqueoussolution to form an intermediate material that will become a mesoporousaluminosilicate zeolite. It should be appreciated that other precursormaterials that include silica, titania, or alumina may be utilized. Forexample, in other embodiments, tetra ethyl orthosilicate and cationicpolymers may be combined to form an intermediate material that willbecome a silicate mesoporous zeolite; or tetra ethyl orthosilicate,tetrabutylorthotitanate, and cationic polymer may be combined to form anintermediate material that will become a titanosilicate mesoporouszeolite. Optionally, the combined mixture may be heated to form theintermediate material, and may crystallize under autoclave conditions.The intermediate material may comprise micropores, and the cationicpolymer may act as a structure-directing agent in the formation of themicropores during crystallization. The intermediate materials may stillcontain the cationic polymers which may at least partially define thespace of the mesopores following their removal. The products may becentrifuged, washed, and dried, and finally, the polymer may be removedby a calcination step. The calcination step may comprise heating attemperatures of at least about 400° C., 500° C., 550° C., or evengreater. Without being bound by theory, it is believed that the removalof the polymers forms at least a portion of the mesopores of themesoporous zeolite, where the mesopores are present in the space onceinhabited by the polymers.

The precursor materials of the mixture, or reagents of the sol-gel,generally determine the material composition of the mesoporous zeolites,such as an aluminosilicate, a titanosilicate, or a pure silicate. Analuminosilicate mesoporous zeolite may comprise a molar ratio of Si/Alof greater than or equal to 10 and less than 10,000, greater than orequal to 25 and less than 10,000, greater than or equal to 50 and lessthan 10,000, greater than or equal to 100 and less than 10,000, greaterthan or equal to 200 and less than 10,000, greater than or equal to 500and less than 10,000, greater than or equal to 1,000 and less than10,000, or even greater than or equal to 2,000 and less than 10,000. Ina pure silicate zeolite, a negligible amount or no amount of aluminum ispresent in the framework of the zeolite, and the Si/Al molar ratiotheoretically approaches infinity. As used herein a “pure silicate”refers to a material comprising at least about 99.9 weight percent (wt.%) of silicon and oxygen atoms in the framework of the zeolite. Othermaterials, including water and sodium hydroxide, may be utilized duringthe formation of the material but are not present in the framework ofthe zeolite. A pure silica mesoporous zeolite may be formed by utilizingonly silicon-containing materials to form the framework of the zeoliteand no aluminum. A titanosilicate porous structure may comprise a molarratio of Si/Ti of greater than or equal to 30 and less than 10,000,greater than or equal to 40 and less than 10,000, greater than or equalto 50 and less than 10,000, greater than or equal to 100 and less than10,000, greater than or equal to 200 and less than 10,000, greater thanor equal to 500 and less than 10,000, greater than or equal to 1,000 andless than 10,000, or even greater than or equal to 2,000 and less than10,000. It has been found that PDAMAB-TPHAB cationic polymer, describedherein, may be utilized to form mesoporous ZSM-5 zeolites when used withsilica and alumina precursor materials, mesoporous TS-1 zeolites whenused with a silica and titania precursor, and mesoporous silicalite-Izeolites when used with silica precursors. It has also been found thatPDAMAB-TMHAB may be utilized to form mesoporous Beta zeolites when usedwith silica and alumina precursors.

The cationic polymers presently disclosed may comprise one or moremonomers which each comprise multiple cationic functional groups, suchas quaternary ammonium cations or quaternary phosphonium cations. Thecation functional groups of the monomers may be connected by ahydrocarbon chain. Without being bound by theory, it is believed thatthe cationic functional groups may form or at least partially aid informing the microstructure of the mesoporous zeolite (for example, anMFI framework type or BEA framework type) and the hydrocarbon chains andother hydrocarbon functional groups of the polymer may form or at leastpartially aid in forming the mesopores of the mesoporous zeolite.

The cationic polymers may comprise functional groups which are utilizedas SDAs for the fabrication of the zeolite microstructure. Suchfunctional groups, which are believed to form the zeolitemicrostructure, include quaternary ammonium cations and quaternaryphosphonium cations. Quaternary ammonium is generally depicted inChemical Structure #1 and quaternary phosphonium is generally depictedin Chemical Structure #2.

As used throughout this disclosure, the encircled plus symbols (“+”)show cationic positively charged centers. R groups (including R1, R2,R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, and R13) represent chemicalconstituents. One or more of the various R groups may be structurallyidentical or may be structurally different from one another.

In Chemical Structure #1 and Chemical Structure #2, R1, R2, R3, and R4may include hydrogen atoms or hydrocarbons, such as a hydrocarbon chain,optionally comprising one or more heteroatoms. As used throughout thisdisclosure, a “hydrocarbon” refers to a chemical or chemical moietycomprising hydrogen and carbon. For example, the hydrocarbon chain maybe branched or unbranched, and may comprise an alkane hydrocarbon chain,an alkene hydrocarbon chain, or an alkyne hydrocarbon chain, includingcyclic or aromatic moieties. In some embodiments, one or more of R1, R2,R3, or R4 may represent hydrogen atoms. As used throughout thisdisclosure, a heteroatom is a non-carbon and non-hydrogen atom. Inembodiments, quaternary ammonium and quaternary phosphonium may bepresent in a cyclic moiety, such as a five-atom ring, a six-atom ring,or a ring comprising a different number of atoms. For example, inChemical Structure #1 and Chemical Structure #2, the R1 and R2constituents may be part of the same cyclic moiety.

In one or more embodiments, the two cation moieties may form ionic bondswith anions. Various anionic chemical species are contemplated,including Cl⁻, Br⁻, F⁻, I⁻, OH⁻, ½SO₄ ²⁻, ⅓PO₄ ³⁻, ½S²⁻, AlO₂ ⁻, BF₄ ⁻,SbF₆ ⁻, and BArF⁻. In some embodiments, an anion with a negative chargeof more than 1-, such as 2-, 3-, or 4-, may be utilized, and in thoseembodiments, a single anion may pair with multiple cations of thecationic polymer. As used throughout this disclosure, a fraction listedbefore an anionic composition means that the anion is paired with morethan one cation and may, for example, be paired with the number ofcations equal to its negative charge.

In one or more embodiments, two cations of a monomer may be separatedfrom one another by a hydrocarbon chain. The hydrocarbon chain may bebranched or unbranched, and may comprise an alkane hydrocarbon chain, analkene hydrocarbon chain, or an alkyne hydrocarbon chain, includingcyclic or aromatic moieties. In one embodiment, the length of thehydrocarbon chain (measured as the number of carbons in the chaindirectly connecting the two cations) may be from 1 to 10,000 carbonatoms, such 1 to 20 carbon atom alkane chains.

The cationic polymers described in this disclosure are generallynon-surfactants. A surfactant refers to a compound that lowers thesurface tension (or interfacial tension) between two liquids or betweena liquid and a solid, usually by the inclusion of a hydrophilic head anda hydrophobic tail. Non-surfactants do not contain such hydrophobic andhydrophilic regions, and do not form micelles in a mixture containing apolar material and non-polar material. Without being bound by theory, itis believed that the polymers described are non-surfactants because ofthe inclusion of two or more cation moieties which are joined by ahydrocarbon chain. Such an arrangement has polar charges on or near eachend of the monomer, and such an arrangement excludes the hydrophobicsegment from the polymer, and thus the surfactant behavior(self-assembly in solution). On the atomic scale, it is believed thatthe functional groups (for example, quaternary ammoniums) on the polymerdirect the formation of zeolite structure; on the mesoscale, the polymerfunctions simply as a “porogen” rather than a structure directing agentin the conventional sense. As opposed to the cases of surfactants,non-surfactant polymers do not self-assemble to form an orderedmesostructure, which in turn favors the crystallization of zeolites,producing a new class of hierarchical zeolites that featurethree-dimensionally (3-D) continuous zeolitic frameworks with highlyinterconnected intracrystalline mesopores.

In one embodiment, the cationic polymer may comprise the generalizedstructure depicted in Chemical Structure #3:

Chemical Structure #3 depicts a single monomer of the cationic polymer,which is signified by the included bracket, where n is the total numberof repeating monomers in the polymer. In some embodiments, the cationicpolymer may be a copolymer comprising two or more monomer structures.The X⁻ and Y⁻ of Chemical Structure #3 represent anions. It should beunderstood that one or more monomers (such as that shown in ChemicalStructure #3) of the cationic polymers described in the presentapplication may be different from one another. For example, variousmonomer units may include different R groups. Referring to ChemicalStructure #3, A may represent nitrogen or phosphorus and B may representnitrogen or phosphorus, R5 may be a branched or unbranched hydrocarbonchain having a carbon chain length of from 1 to 10,000 carbon atoms,such as a 2 to 20 carbon alkane, X⁻ may be an anion and Y⁻ may be ananion, and R6, R7, R8, R9, R10, R11, R12, and R13 may be hydrogen atomsor hydrocarbons optionally comprising one or more heteroatoms.

Referring to Chemical Structure #3, in one or more embodiments, A mayrepresent nitrogen or phosphorus and B may represent nitrogen orphosphorus. In one embodiment, A and B may be nitrogen, and in anotherembodiment, A and B may be phosphorus. For example, A of ChemicalStructure #3 may comprise a quaternary ammonium cation or a quaternaryphosphonium cation. As shown in Chemical Structure #3, A may be aportion of a ring structure, such as a five-sided ring. In one or moreembodiments, X⁻ and Y⁻ are anions. For example, X⁻ may be chosen fromCl⁻, Br⁻, F⁻, I⁻, OH⁻, ½SO₄ ²⁻, ⅓PO₄ ³⁻, ½S²⁻, AlO₂ ⁻, BF₄ ⁻, SbF₆ ⁻,and BArF⁻, and Y⁻ may be chosen from Cl⁻, Br⁻, F⁻, I⁻, OH⁻, ½SO₄ ²⁻,⅓PO₄ ³⁻, ½S₂ ⁻, AlO₂ ⁻, BF₄ ⁻, SbF₆ ⁻, and BArF⁻. In embodiments, ananion with a negative charge of more than 1-, such as 2-, 3-, or 4-, maybe present, and in those embodiments, a single anion may pair withmultiple cations of the cationic polymer.

Still referring to Chemical Structure #3, R5 represents a branched orunbranched hydrocarbon chain. The hydrocarbon chain may be branched orunbranched, and may comprise an alkane hydrocarbon chain, an alkenehydrocarbon chain, or an alkyne hydrocarbon chain. The length of thehydrocarbon chain (measured as the number of carbons in the chaindirectly connecting A to B) may be from 1 to 10,000 carbon atoms (suchas from 1 to 1,000 carbon atoms, from 1 to 500 carbon atoms, from 1 to250 carbon atoms, from 1 to 100 carbon atoms, from 1 to 50 carbon atoms,from 1 to 25 carbon atoms, from 1 to 20 carbon atoms, from 1 to 15carbon atoms, from 1 to 10 carbon atoms, from 2 to 10,000 carbon atoms,from 3 to 10,000 carbon atoms, from 4 to 10,000 carbon atoms, from 5 to10,000 carbon atoms, from 6 to 10,000 carbon atoms, from 8 to 10,000carbon atoms, from 10 to 10,000 carbon atoms, from 15 to 10,000 carbonatoms, from 20 to 10,000 carbon atoms, from 25 to 10,000 carbon atoms,from 50 to 10,000 carbon atoms, from 100 to 10,000 carbon atoms, from250 to 10,000 carbon atoms, from 500 to 10,000 carbon atoms, from 2 to100 carbon atoms, from 3 to 30 carbon atoms, from 4 to 15 carbon atoms,or from 5 to 10 carbon atoms, such as 6 carbon atoms. R5 may compriseone or more heteroatoms, but some embodiments of R5 include only carbonand hydrogen.

In Chemical Structure #3, R6, R7, R8, R9, R10, R11, R12, and R13 may behydrogen atoms or hydrocarbons optionally comprising one or moreheteroatoms, respectively. For example, some of R6, R7, R8, R9, R10,R11, R12, and R13 may be structurally identical with one another andsome of R6, R7, R8, R9, R10, R11, R12, and R13 may be structurallydifferent from one another. For example, one or more of R6, R7, R8, R9,R10, R11, R12, and R13 may be hydrogen, or alkyl groups, such as methylgroups, ethyl groups, propyl groups, butyl groups, or pentyl groups. Inembodiments, one or more of R6, R7, R8, and R9 may be hydrogen. Inembodiments, one or more of R10, R11, R12, and R13 may be an alkylgroups. For example, R10 may be a methyl, ethyl, propyl, or butyl group,and one or more of R11, R12, and R13 may be methyl, ethyl, propyl, orbutyl groups. In one embodiment, R10 is a methyl group and R11, R12, andR13 are propyl groups. In one embodiment, R11, R12, and R13 are methylgroups. In another embodiment, R11, R12, and R13 are ethyl groups. Inanother embodiment, R11, R12, and R13 are propyl groups.

In one or more embodiments, Chemical Structure #3 may be a polymer thatcomprises n monomer units, where n may be from 10 to 10,000,000 (such asfrom 50 to 10,000,000, from 100 to 10,000,000, from 250 to 10,000,000,from 500 to 10,000,000, from 1,000 to 10,000,000, from 5,000 to10,000,000, from 10,000 to 10,000,000, from 100,000 to 10,000,000, from1,000,000 to 10,000,000, from 10 to 1,000,000, from 10 to 100,000, from10 to 10,000, from 10 to 5,000, from 10 to 1,000, from 10 to 500, from10 to 250, or from 10 to 100. For example, n may be from 1,000 to1,000,000.

According to one or more embodiments, the cationic polymer comprisespoly(N¹,N¹-diallyl-N-alkyl-N⁶,N⁶,N⁶-trialkylalkane-1,6-diamoniumhalide), such aspoly(N¹,N¹-diallyl-N¹-methyl-N⁶,N⁶,N⁶-trialkylhexane-1,6-diamoniumbromide). An example of such ispoly(N¹,N¹-diallyl-N-methyl-N⁶,N⁶,N⁶-tripropylhexane-1,6-diamoniumbromide), referred to as (PDAMAB-TPHAB) and shown in Chemical Structure#4.

In another embodiment, the cationic polymer comprisespoly(N¹,N¹-diallyl-N¹-methyl-N⁶,N⁶,N⁶-triethylhexane-1,6-diamoniumbromide), referred to as (PDAMAB-TEHAB) and shown in Chemical Structure#5.

In another embodiment, the cationic polymer comprisespoly(N¹,N¹-diallyl-N¹-methyl-N⁶,N⁶,N⁶-trimethylhexane-1,6-diamoniumbromide), referred to as (PDAMAB-TMHAB) and shown in Chemical Structure#6.

The cationic polymers described in the present disclosure, includingthat of Chemical Structure #3, may be synthesized by a reaction pathwaysuch as that shown in FIG. 1 . Specifically, FIG. 1 depicts a reactionpathway for the synthesis of PDAMAB-TPHAB. However, it should beunderstood that other reaction pathways may be utilized for thesynthesis of PDAMAB-TPHAB or other generalized polymers such as thepolymer of Chemical Structure #3. Furthermore, it should be understoodthat the reaction scheme depicted in FIG. 1 may be adapted to formpolymers which have a different structure than PDAMAB-TPHAB, such assome polymers included in the generalized Chemical Structure #3 (forexample, PDAMAB-TEHAB or PDAMAB-TEHAB. For example, the hydrocarbonchain length between the cation groups A and B of Chemical Structure #3may be changed by utilizing a different reactant in the scheme of FIG. 1.

Referring to FIG. 1 , the cationic polymer of Chemical Structure #3 maybe formed by a process comprising forming a diallyl methyl ammoniumhydrochloride cation with a chloride anion from diallylamine,polymerizing the diallyl methyl ammonium hydrochloride to form apoly(diallyl methyl ammonium hydrochloride) (PDMAH), forming apoly(diallyl methyl amine) (PDMA) from the poly(diallyl methyl ammoniumhydrochloride) (PDMAH), forming an ammonium halide cation with a halideanion by reacting a trialkyl amine, such as a tripropyl amine, with adihaloalkane, and forming the PDAMAB-TPHAB by reacting the PDMA with theammonium halide cation. In other embodiments, triethyl amine ortrimethyl amine may be utilized as the trialkyl amine.

Still referring to FIG. 1 , according to one or more embodiments, thediallyl methyl ammonium hydrochloride cation with a chloride anion maybe formed by contacting the diallylamine with formic acid, formaldehyde,and HCl. In other embodiments, the diallyl methyl ammonium hydrochloridemay be polymerized by contact with 2,2′-axobis(2-methylpropionamidine)dihydrochloride (AAPH). In additional embodiments, the poly(diallylmethyl amine) (PDMA) may be formed by contacting the poly(diallyl methylammonium hydrochloride) (PDMAH) with methane and sodium methoxide.

According to another embodiment, the cationic polymer may be aco-polymer comprising the monomer of the structure depicted in ChemicalStructure #3 and the monomer of Chemical Structure #7.

Referring to Chemical Structure #7, in one or more embodiments, A mayrepresent nitrogen or phosphorus. In one embodiment, A may be nitrogen,and in another embodiment, A may be phosphorus. For example, A ofChemical Structure #7 may comprise a quaternary ammonium cation or aquaternary phosphonium cation. As shown in Chemical Structure #7, A maybe a portion of a ring structure, such as a five-sided ring. Anions maybe present and be attracted to A or B, or both, for example, anions maybe chosen from Cl⁻, Br⁻, F⁻, I⁻, OH⁻, ½SO₄ ²⁻, ⅓PO₄ ³⁻, ½S²⁻, AlO₂ ⁻,BF₄ ⁻, SbF₆ ⁻, and BArF⁻. In embodiments, an anion with a negativecharge of more than 1-, such as 2-, 3-, or 4-, may be present, and inthose embodiments, a single anion may pair with multiple cations of thecationic polymer.

In Chemical Structure #3, R6, R7, R8, R9, R10, may be hydrogen atoms orhydrocarbons optionally comprising one or more heteroatoms,respectively. For example, some of R6, R7, R8, R9, R10 may bestructurally identical with one another and some of R6, R7, R8, R9, R10may be structurally different from one another. For example, one or moreof R6, R7, R8, R9, R10, may be hydrogen, or alkyl groups, such as methylgroups, ethyl groups, propyl groups, butyl groups, or pentyl groups. Inembodiments, one or more of R6, R7, R8, and R9 may be hydrogen. Inembodiments, R10 may be an alkyl group. For example, R10 may be amethyl, ethyl, propyl, or butyl group. In one embodiment, R10 is amethyl group.

An embodiment of cationic polymers comprising the monomer of thestructure depicted in Chemical Structure #3 and the monomer of Chemicalstructure #7 is depicted in Chemical Structure #8.

As depicted in Chemical Structure #8, the co-polymer may include themonomeric component of Chemical Structure #3 in “m” parts and themonomeric component of Chemical structure #7 in “o” parts. According toembodiments, the ratio of m/(o+m) may be equal to from 0 to 100%. Forexample, when m/(o+m)=0%, the cationic polymer may include only themonomeric components depicted in Chemical Structure #7, and whenm/(o+m)=100%, the cationic polymer may include only the monomericcomponents depicted in Chemical Structure #3. In additional embodiments,m/(o+m) may be equal to from 0 to 25%, from 25% to 50%, from 50% to 75%,or from 75% to 100%. In some embodiments, m/(o+m) may be equal to from25% to 75%, or from 60% to 70%.

In one or more embodiments, Chemical Structure #7 may be a co-polymerthat comprises (o+m) monomer units, where (o+m) may be from 10 to10,000,000 (such as from 50 to 10,000,000, from 100 to 10,000,000, from250 to 10,000,000, from 500 to 10,000,000, from 1,000 to 10,000,000,from 5,000 to 10,000,000, from 10,000 to 10,000,000, from 100,000 to10,000,000, from 1,000,000 to 10,000,000, from 10 to 1,000,000, from 10to 100,000, from 10 to 10,000, from 10 to 5,000, from 10 to 1,000, from10 to 500, from 10 to 250, or from 10 to 100. For example, (o+m) may befrom 1,000 to 1,000,000.

The monomer of Chemical Structure #8 may, in one embodiment, be formedby supplying a lesser molar amount of ammonium halide cation, such thatonly a portion of the PDMA reacts with ammonium halide cation. In suchan embodiment, the non-cation substituted PDMA monomers arerepresentative of the monomers of Chemical Structure #7 and the cationsubstituted monomers are representative of the monomers of ChemicalStructure #3.

According to one or more embodiments disclosed herein, the zeolitesdescribed above, either mesoporous zeolites or conventionalnon-mesoporous zeolites may serve as an “initial zeolite” which is thendehydroxylated, forming a dehydroxylated zeolite. In general, theinitial zeolite may refer to a zeolite which is not substantiallydehydroxylated and includes at least a majority of vicinal hydroxylgroups. Dehydroxylation, as is commonly understood by those skilled inthe art, involves a reaction whereby a water molecule is formed by therelease of a hydroxyl group and its combination with a proton. Theinitial zeolite may primarily comprise vicinal silanol functionalities.In one or more embodiments, dehydroxylating the initial zeolite may formisolated terminal silanol functionalities comprising hydroxyl groupsbonded to silicon atoms of the microporous framework of thedehydroxylated zeolite. Such isolated silanol functionalities may beexpressed as ≡Si—O—H.

As described herein “silanol functionalities” refer to ≡Si—O—H groups.Silanol groups generally include a silicon atom and a hydroxyl group(—OH). As described herein, “terminal” functionalities refer to thosethat are bonded to only one other atom. For example, the silanolfunctionality may be terminal by being bonded to only one other atomsuch as a silicon atom of the microporous framework. As describedherein, “isolated silanol functionalities” refer to silanolfunctionalities that are sufficiently distant from one another such thathydrogen-bonding interactions are avoided with other silanolfunctionalities. These isolated silanol functionalities are generallysilanol functionalities on the zeolite that are non-adjacent to othersilanol functionalities. Generally, in a zeolite that includes siliconand oxygen atoms, “adjacent silanols” are those that are directly bondedthrough a bridging oxygen atom. Isolated silanol functionalities may beidentified by FT-IR and/or ¹H-NMR, as would be understood by thoseskilled in the art. For example, isolated silanol functionalities may becharacterized by a sharp and intense FT-IR band at about 3749 cm⁻¹and/or a ¹H-NMR shift at about 1.8 ppm. In the embodiments describedherein, peaks at or near 3749 cm⁻¹ in FT-IR and/or at or near 1.8 ppm in¹H-NMR may signify the existence of the dehydroxylated zeolite, and thelack of peaks at or near these values may signify the existence of theinitial zeolite.

Isolated silanol functionalities can be contrasted with vicinal silanolfunctionalities, where two silanol functionalities are “adjacent” oneanother by each being bonded with a bridging oxygen atom. ChemicalStructure #9 depicts an isolated silanol functionality and ChemicalStructure #10 depicts a vicinal silanol functionality. Hydrogen bondingoccurs between the oxygen atom of one silanol functionality and thehydrogen atom of an adjacent silanol functionality in the vicinalsilanol functionality. Vicinal silanol functionality may show adifferent band in FT-IR and ¹H-NMR, such as 3520 cm⁻¹ or 3720 cm⁻¹ inFT-IR, and 2.7 ppm in ¹H-NMR.

As described herein, a “dehydroxylated zeolite” refers to a zeoliticmaterial that has been at least partially dehydroxylated (i.e., H and Oatoms are liberated from the initial zeolite and water is released).Without being bound by theory, it is believed that the dehydroxylationreaction forms a molecule of water from a hydroxyl group of a firstsilanol and a hydrogen of a second silanol of a zeolite. The remainingoxygen atom of the second silanol functionality forms a siloxane groupin the zeolite (i.e., (≡Si—O—S≡), sometimes referred to as strainedsiloxane bridges. Generally, strained siloxane bridges are those formedin the dehydroxylation reaction and not in the formation of the initialzeolite.

In one or more embodiments, the initial zeolite (as well as thedehydroxylated zeolite) comprises aluminum in addition to silicon andoxygen. For example, ZSM-5 zeolite may include such atoms. Inembodiments with aluminum present, the microporous framework of thedehydroxylated zeolite may include Bronsted acid silanolfunctionalities. In the Bronsted acid silanol functionalities, eachoxygen atom of the Bronsted acid silanol functionality may bridge asilicon atom and an aluminum atom of the microporous framework. SuchBronsted acid silanol functionalities may be expressed as[≡Si—O(H)→Al≡].

Chemical Structure #11 depicts an example of an aluminosilicate zeoliteframework structure that includes the isolated terminal silanolfunctionalities and Bronsted acid silanol functionalities describedherein.

According to one or more embodiments, the dehydroxylation of the initialzeolite may be performed by heating the initial zeolite at elevatedtemperatures under vacuum, such as from 700° C. to 1100° C. It isbelieved that according to one or more embodiments described herein,heating at temperatures below 650° C. may be insufficient to formterminal isolated silanol functionalities. However, heating attemperatures greater than 1100° C. may result in the elimination ofterminal isolated silanol functionalities, or the production of suchfunctionalities in low enough concentrations that further processing bycontact with organometallic chemicals to form organometallic moieties isnot observed, as is described subsequently herein.

According to embodiments, the temperature of heating may be from 650° C.to 700° C., from 700° C. to 750° C., from 750° C. to 800° C., from 800°C. to 850° C., from 850° C. to 900° C., from 900° C. to 950° C., from950° C. to 1000° C., from 1000° C. to 1050° C., from 1050° C. to 1100°C., or any combination of these ranges. For example, temperature rangesfrom 650° C. to any named value are contemplated, and temperature rangesfrom any named value to 1100° C. are contemplated. As described herein,vacuum pressure refers to any pressure less than atmospheric pressure.According to some embodiments, the pressure during the heating processmay be less than 10⁻² mbar, less than 10^(−2.5) mbar, less than 10⁻³mbar, less than 10^(−3.5) mbar, less than 10⁻⁴ mbar, or even less than10^(−4.5) mbar. The heating times may be sufficiently long such that thezeolite is brought to thermal equilibrium with the oven or other thermalapparatus utilized. For example, heating times of greater than 8 hours,greater than 12 hours, or greater than 18 hours may be utilized. Forexample, 24 hours of heating time may be utilized.

Without being bound by any particular theory, it is believed thatgreater heating temperatures during dehydroxylation correlate withreduced terminal silanols present on the dehydroxylated zeolite.However, it is believed that greater heating temperatures duringdehydroxylation correlate with greater amounts of strained siloxanes.For example, when the initial zeolite is heated at 700° C. duringdehydroxylation, the concentration of isolated terminal silanol groupsmay be at least 0.4 mmol/g, such as approximately 0.45 mmol/g in someembodiments, as measured by methyl lithium titration. Dehydroxylating at1100° C. may result in much less isolated terminal silanol and much lessisolated Bronsted acid silanol. In some embodiments, less than 10% ofthe isolated terminal silanol groups present at 700° C. dehydroxylationare present when 1100° C. dehydroxylation heating is used. However, itis believed that strained siloxane groups are appreciably greater atthese greater dehydroxylation temperatures.

According to one or more of the embodiments disclosed herein, thedehydroxylated zeolite is reacted with an organometallic chemical. Thisprocess may be referred to as the organometallic moiety grafting step.As presently described, an “organometallic chemical” refers to anychemical comprising both metal and organic constituents, as would beunderstood by one skilled in the art. The organometallic moietiesgrafted to the zeolitic framework structure comprise a portion of theorganometallic chemical. The organometallic chemical, as describedherein, can be thought of as a precursor to the grafted organometallicmoiety. According to embodiments, the organometallic chemical reactswith the dehydroxylated zeolite to form the organometallic moiety. Thereacting of the organometallic chemical with the dehydroxylated zeolitemay form the modified zeolite comprising organometallic moieties. Eachof the organometallic moieties may be bonded to an oxygen atom of themodified zeolite. As presently described, the “organometallic moiety”may be any chemical group comprising a metal atom and some organicconstituent. Generally, the metal atom of the organometallic moiety maybe bonded to a bridging oxygen atom. The organometallic moieties, asdescribed herein, may be derived from an organometallic chemical that isreacted with the dehydroxylated zeolite.

Chemical Structure #12, shown below, generally depicts one reactionwhich is contemplated to take place when the dehydroxylated zeolite iscontacted by the organometallic chemical. In Chemical Structure #12,MR₁R₂R₃R₄ is representative of an organometallic chemical, where M is ametal atom and R₁, R₂, R₃, and R₄ are ligands bonded to the metal. Itshould be understood that, depending upon the metal, less than four orgreater than four ligands may be present in the organometallic chemical.Still referring to Chemical Structure #12, the organometallic chemicalis reacted with the dehydroxylated zeolite and the resulting modifiedzeolite includes the organometallic moiety. The organometallic moiety isgenerally shown as -MR₂R₃R₄. In the grafting reaction of ChemicalStructure #12, the R₁ ligand is bonded with a hydrogen atom of ahydroxyl group of the dehydroxylated zeolite and forms a bi-productdepicted in Chemical Structure #12 as R₁—H. As depicted, the modifiedzeolite may include the organometallic moiety each bonded to bridgingoxygen atoms. The bridging oxygen atom may bridge the metal atom of theorganometallic moiety and a silicon atom of the microporous framework ofthe modified zeolite. As described herein, “bridging” atoms are thosewhich are bonded to at least two other atoms. For example, the bridgingoxygen atoms described herein may be bonded with a silicon atom of themicroporous framework as well as the metal atom of the organometallicmoiety. Bridging atoms may be contrasted with terminal atoms ormoieties, which are only bonded to a single other atom. As used herein,“bridging” refers to direct bonding to the two or more other atoms ormoieties.

According to one or more of the embodiments disclosed herein, theorganometallic moiety grafting step, as depicted in Chemical Structure#12, may take place by liquid impregnation of the organometallicchemical. The organometallic chemical may be in a solution with a drysolvent such as n-pentane. In some embodiments, the impregnation processmay be performed at or near room temperature under stirring for severalhours, such as from 3 to 10 hours. Following impregnation, the modifiedzeolite may be washed and dried. Other grafting methods are contemplatedbesides wet impregnation, and the grafting technique should not benecessarily limiting on the modified zeolite structure or methods ofmaking such. For example, in one or more embodiments, the organometallicmoiety grafting step may take place by sublimation of the organometalliccompound if the organometallic compound is sufficiently volatile.

Without being bound by theory, it is believed that the organometallicmoiety grafting described herein, where organometallic moieties arebonded to bridging oxygen atoms, may take place only when isolatedterminal silanol groups are present on the zeolite. Thus, it is believedthat methods which do not utilize a dehydroxylation step which promotesthe formation of isolated terminal silanol functionalities will not besuccessful in organometallic moiety grafting as presently disclosed.

In one or more embodiments, substantially all of the isolated terminalsilanol groups of the dehydroxylated zeolite may be reacted. Forexample, if the concentration of isolated terminal silanol groups is atleast 0.4 mmol/g, the concentration of organometallic moieties may be atleast 0.4 mmol/g. It is also contemplated that, according to someembodiments, not all isolated terminal silanol groups are reacted.According to embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90%, at least 95%, or at least 99% of isolatedterminal silanol groups of the dehydroxylated zeolite are reacted in theorganometallic grafting step. According to one or more embodiments, themodified zeolite may comprise at least 0.25 mmol/g, at least 0.3 mmol/g,at least 0.35 mmol/g, at least 0.4 mmol/g, or even at least 0.45 mmol/gof the organometallic moieties.

In one or more embodiments, since the organometallic moiety of themodified zeolite is bonded with an oxygen from an isolated terminalsilanol group of the dehydroxylated zeolite, dehydroxylation conditionsthat form relatively greater amounts of isolated terminal silanol groupsmay be desired. For example, as described herein, temperatures near 7000(such as 650° C. to 900° C.) for dehydroxylation may be utilized to formgreater amounts of isolated terminal silanol groups. In one or moreembodiments, dehydroxylation heating temperatures may be less than orequal to 900° C., less than or equal to 850° C., less than or equal to800° C., or less than or equal to 750° C.

In one or more embodiments, the organometallic moieties may comprisehafnium. In one or more embodiments, the organometallic moieties maycomprise a hafnium compound that may have a chemical formula ofHfR₁R₂R₃. In one or more embodiments R₁ may be a functional group. Forexample, R₁ may be an alkyl group, a hydride group, a hydroxyl group, analkoxy group, an allyl group, a cyclopentadienyl group, an amino group,an amido group, an imido group, a nitrido group, a carbene group, acarbyne group, a halide group, a benzyl group, a phenyl group, or anoxide group. In one or more embodiments, R₂ may be a functional group.For example, R₂ may be an alkyl group, a hydride group, a hydroxylgroup, an alkoxy group, an allyl group, a cyclopentadienyl group, anamino group, an amido group, an imido group, a nitrido group, a carbenegroup, a carbyne group, a halide group, a benzyl group, a phenyl group,or an oxide group. In one or more embodiments, R₃ may be a functionalgroup. For example, R₃ may be an alkyl group, a hydride group, ahydroxyl group, an alkoxy group, an allyl group, a cyclopentadienylgroup, an amino group, an amido group, an imido group, a nitrido group,a carbene group, a carbyne group, a halide group, a benzyl group, aphenyl group, or an oxide group.

In one or more embodiments, each of R₁, R₂, and R₃ may be an alkylgroup. In one or more embodiments, each of R₁, R₂, and R₃ may be thesame alkyl group. In one or more embodiments, R₁, R₂, and R₃ may be aneopentyl group. In one or more embodiments, the organometallic moietiesmay comprise tris(neopentyl)hafnium.

In one or more embodiments, organometallic moieties and organometallicchemicals may comprise one or more functional groups. As describedherein, a “parent” atom or molecule refers to the atom or molecule towhich a described functional group or other moiety is bonded. In one ormore embodiments, the parent atom or molecule may comprise hafnium.

As described herein, an “alkyl group” may be a functional group derivedfrom an alkane. Generally, alkanes may be saturated hydrocarbons thatmay contain carbon-carbon single bonds. In one or more embodiments, analkyl group may derive from an alkane comprising one or more carbonatoms. For example, the alkyl group may comprise a methyl, ethyl,propyl, butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, or n-decylgroup. In one or more embodiments, the alkyl group may be derived from abranched alkane of at least three carbon atoms. For example, the alkylgroup may comprise an isopropyl, isobutyl, tertbutyl, isopentyl, orneopentyl group. In one or more embodiments, alkyl groups may have oneor more isomers and, any isomers of an alkyl group may be bound to theparent atom. In one or more embodiments, the alkyl group may comprise acycloalkane. For example, the alkyl group may comprise a cyclobutyl,cyclopentyl, cyclohexyl, cyclooctyl, cyclononyl, or cyclodecyl group.

As described herein, a “hydride group” may be a hydrogen atom with anegative formal charge. In one or more embodiments the hydride group mayhave nucleophilic, reducing, or basic properties.

As described herein, a “hydroxyl group” may be a functional group thatmay comprise oxygen bonded to hydrogen. In one or more embodiments, ahydroxyl group may have the chemical formula OH. In one or moreembodiments, the oxygen atom of the hydroxyl group may be bonded to theparent atom or molecule.

As described herein, an “alkoxy group” may be a functional group withthe chemical formula OR, where R comprises an alkyl group. In one ormore embodiments, the oxygen atom of the alkoxy group may be bonded tothe parent atom or molecule.

As described herein, an “allyl group” may be a functional groupcomprising a methylene bridge between a vinyl group and the parent atomor molecule. In one or more embodiments, an allyl group may have thechemical formula H₂C═CH—CH₂R, where R is the parent atom or molecule.

As described herein, a “cyclopentadienyl group” may be a functionalgroup comprising an aromatic with the chemical formula [C₅H₅]⁻. In oneor more embodiments, one or more of the hydrogen atoms of thecyclopentadienyl group may be replaced by one or more functional groups.For example, the cyclopentadienyl group may be a pentamethylcyclopentadienyl group or substituted cyclopentadienyl group. In one ormore embodiments, the parent atom or molecule may replace one of thehydrogen atoms in the cyclopentadienyl group. In one or moreembodiments, the parent atom or molecule may comprise a metal and mayform an organometallic complex with the cyclopentadienyl group withoutreplacing one of the hydrogen atoms of the cyclopentadienyl group.

As described herein, an “amino group” may be a functional groupcomprising a nitrogen atom where the nitrogen atom is bonded to theparent atom or molecule. In one or more embodiments, the amino group mayhave a chemical formula of NR₁R₂, where R₁ may be an organic functionalgroup or a hydrogen atom and R₂ may be an organic functional group or ahydrogen atom. In one or more embodiments, R₁ and R₂ may be methylgroups. In one or more embodiments, R₁ and R₂ may be hydrogen atoms.

As described herein, an “amido group” may be a functional group having achemical formula of C(═O)NR₁R₂, where R₁ may be an organic functionalgroup or a hydrogen atom and R₂ may be an organic functional group or ahydrogen atom. In one or more embodiments, R₁ and R₂ may be methylgroups. In one or more embodiments, R₁ and R₂ may be hydrogen atoms. Inone or more embodiments, the carbon atom may be bonded to the parentatom or molecule.

As described herein, an “imido group” may be a functional groupcomprising a nitrogen atom bonded to two acyl groups. As describedherein, an “acyl group” may be a functional group comprising an oxygenatom bonded to an alkyl group by a double bond. In one or moreembodiments, the nitrogen atom of the imido group may be bonded to theparent atom or molecule. In one or more embodiments, the imido group maybe a cyclic functional group.

As described herein, a “nitrido group” may be a functional groupcomprising a nitrogen atom that may have an oxidation state of −3. Inone or more embodiments, the nitrogen atom may be bonded to the parentatom or molecule. In one or more embodiments, the nitrido group maycomprise a nitrogen atom bonded only to transition metals.

As described herein, a “carbene group” may be a functional groupcomprising a carbon atom with two unshared valence electrons. In one ormore embodiments, the carbon atom with two unshared valence electronsmay be bonded to the parent atom or molecule by a single covalent bond.In one or more embodiments, the carbon atom with two unshared valenceelectrons may be bonded to the parent atom or molecule by a doublecovalent bond.

As described herein, a “carbyne group” may be a functional groupcomprising a carbon atom with three non-bonded electrons. In one or moreembodiments, the carbon atom may be bonded to the parent atom ormolecule by a single covalent bond.

As described herein, a “halogen group” may be a functional groupcomprising fluorine, chlorine, bromine, iodine, or astatine. In one ormore embodiments, a halogen comprising fluorine, chlorine, bromine,iodine, or astatine may be bonded to the parent atom or molecule.

As described herein, a “benzyl group” may be a functional groupcomprising a benzene ring attached to a CH₂ group. In one or moreembodiments, a benzyl group may have the chemical formula C₆H₅CH₂. Inone or more embodiments, one or more of the hydrogen atoms of the benzylgroup may be replaced by one or more functional groups. In one or moreembodiments, the CH₂ group may be bonded to the parent atom or molecule.

As described herein, a “phenyl group” may comprise a benzene ring. Inone or more embodiments, a phenol group may have a chemical formula ofC₆H₅. In one or more embodiments, one or more of the hydrogen atoms ofthe phenyl group may be replaced by one or more functional groups. Inone or more embodiments, a carbon atom of the phenyl group may be bondedto the parent atom or molecule.

As described herein, an “oxide group” may be a functional group that maycomprise oxygen. In one or more embodiments, the oxide group may have achemical formula of R═O, where R is the parent atom or molecule.

In one or more embodiments, the organometallic chemical may comprisehafnium. In one or more embodiments, the organometallic chemical maycomprise a hafnium compound that may have a chemical formula ofHfR₁R₂R₃R₄. In one or more embodiments R₁ may be a functional group. Forexample, R₁ may be an alkyl group, a hydride group, a hydroxyl group, analkoxy group, an allyl group, a cyclopentadienyl group, an amino group,an amido group, an imido group, a nitrido group, a carbene group, acarbyne group, a halide group, a benzyl group, a phenyl group, or anoxide group. In one or more embodiments, R₂ may be a functional group.For example, R₂ may be an alkyl group, a hydride group, a hydroxylgroup, an alkoxy group, an allyl group, a cyclopentadienyl group, anamino group, an amido group, an imido group, a nitrido group, a carbenegroup, a carbyne group, a halide group, a benzyl group, a phenyl group,or an oxide group. In one or more embodiments, R₃ may be a functionalgroup. For example, R₃ may be an alkyl group, a hydride group, ahydroxyl group, an alkoxy group, an allyl group, a cyclopentadienylgroup, an amino group, an amido group, an imido group, a nitrido group,a carbene group, a carbyne group, a halide group, a benzyl group, aphenyl group, or an oxide group. In one or more embodiments, R₄ may be afunctional group. For example, R₄ may be an alkyl group, a hydridegroup, a hydroxyl group, an alkoxy group, an allyl group, acyclopentadienyl group, an amino group, an amido group, an imido group,a nitrido group, a carbene group, a carbyne group, a halide group, abenzyl group, a phenyl group, or an oxide group.

In one or more embodiments, each of R₁, R₂, R₃ and R₄ may be an alkylgroup. In one or more embodiments, each of R₁, R₂, R₃ and R₄ may be thesame alkyl group. In one or more embodiments, R₁, R₂, R₃ and R₄ may be aneopentyl group. In one or more embodiments, the organometallic chemicalmay comprise tetrakis(neopentyl)hafnium.

In one or more embodiments, the organometallic chemical may be any ofthe chemical structures disclosed in Chemical Structures 13-23. Forexample, in one or more embodiments, the organometallic chemical maycomprise phenyl groups, as displayed in Chemical Structure 13. In one ormore embodiments, the organometallic chemical may comprise alkoxy groupsas displayed in Chemical Structures 14-16. In one or more embodiments,the organometallic chemical may comprise amino groups, as displayed inChemical Structures 19-22. In one or more further embodiments, theorganometallic chemical may comprise cyclopentadienyl groups, asdisplayed in Chemical Structures 17-18 and 23.

As previously described herein, zeolites generally comprise crystallineatomic arrangements, as opposed to amorphous arrangement. Without beingbound by theory, it is believed that isolated silanol moieties may notbe formed on non-crystalline materials when heated. As such, it isbelieved that the grafting of the organometallic chemical to form theorganometallic moiety on the modified zeolite may not occur onnon-crystalline materials.

Additionally, as previously disclosed herein, the modified zeolite, aswell as the zeolitic precursors, may comprise mesopores. The mesoporesmay allow for grafting of the organometallic chemicals throughout theinterior of the modified zeolite. In order to access such interiorsites, the mesopores may be at least as large as the organometallicchemical. For example, the average pore size of the modified zeolite(dehydroxylated zeolite or initial zeolite) may be at least 0.5 nm, atleast 1 nm, at least 2 nm, at least 3 nm, at least 4 nm, at least 5 nm,or even at least 10 nm greater than the size of the organometallicchemical.

It should be understood that, according to one or more embodiments,presently disclosed, the various functional groups of the zeolites maybe identified by FT-IR and/or ¹H-NMR methods. When a zeolite “comprises”such a moiety, such inclusion may be evidenced by a peak at or near thebands in FT-IR and/or ¹H-NMR corresponding to such moiety. Suchdetection methods would be understood by those skilled in the art.

In one or more embodiments, the presently disclosed modified zeolitesmay be suitable for use as catalysts in refining, petrochemicals, andchemical processing. For example, zeolites may be useful as crackingcatalysts in processes such as hydrocracking or fluid catalyticcracking. Table 1 shows some contemplated catalytic functionality forthe presently disclosed modified zeolites, and provides the type ofzeolite that may be describable. However, it should be understood thatthe description of Table 1 should not be construed as limiting on thepossible uses for modified zeolites presently disclosed.

TABLE 1 Framework of zeolite components Catalytic Reaction TargetDescription of Catalyst Catalytic cracking To convert high boiling, FAU,MFI high molecular mass hydrocarbon fractions to more valuable gasoline,olefinic gases, and other products Hydrocracking To produce diesel withBEA, FAU higher quality Gas oil hydrotreating/ Maximizing productionFAU, MFI Lube hydrotreating of premium distillate by catalytic dewaxingAlkane cracking and To improve octane and MFI alkylation of productionof gasolines aromatics and BTX Olefin To convert light olefins FER, MFIoligomerization to gasoline & distillate Methanol To produce lightolefins CHA, MFI dehydration from methanol to olefins Heavy aromatics Toproduce xylene FAU, MFI transalkylation from C9+ Fischer-Tropsch Toproduce gasoline, MFI Synthesis FT hydrocarbons, and linearalpha-olefins, mixture of oxygenates CO₂ to fuels and To make organicMFI chemicals chemicals, materials, and carbohydrates

In embodiments where mesopores are present in the modified zeolite,relatively large hydrocarbons, such as vacuum gas oils, may have accessto interior catalytic sites on the modified zeolites. Additionally,since organometallic moieties may be present in the interior regionswhere relatively large hydrocarbons may diffuse, the relatively largehydrocarbons may have additional contacting with the organometallicmoieties, which may promote additional or alternative catalyticfunctionality as compared with the catalytic sites on the zeoliteframework.

According to additional embodiments, the presently disclosed modifiedzeolites may be suitable for use in separation and/or mass captureprocesses. For example, the presently disclosed modified zeolites may beuseful for adsorbing CO₂ and for separating p-xylene from its isomers.

According to embodiments, the metal in the organometallic moiety mayimprove stability of the material, particularly if used as a catalyst.Zeolitic catalysts may be exposed to relatively high heat duringreaction, it is believed that the presently disclosed modified zeolitesmay exhibit less aging and may have a longer service time beforebecoming temporarily or permanently deactivated.

EXAMPLES

The various embodiments of methods and systems for formingfunctionalized zeolites will be further clarified by the followingexamples. The examples are illustrative in nature and should not beunderstood to limit the subject matter of the present disclosure.

Example 1—Synthesis of PDAMAB-TPHAB Cationic Polymer

A generalized reaction sequence for producing PDAMAB-TPHAB is depictedin FIG. 1 . Each step in the synthesis is described in the context ofFIG. 1 .

In a first step, a methyl amine monomer was synthesized. Diallylamine (1part equivalent, 0.1 mol) was slowly added to a solution of formic acid(5 equivalent, 0.5 mol) that was cooled to 0° C. in a 500 milliliter(mL) round-bottom flask. To the resulting clear solution a formaldehydesolution (37% solution; 3 equivalent, 0.3 mol) was added and the mixturewas stirred at room temperature for 1 hour. Then, the flask wasconnected to a reflux condenser and the reaction mixture was heatedovernight at 110° C. After, the solution was cooled and aqueous HCl (4N, 2 equivalent, 0.9 mol, 225 mL) was added. The crude reaction productwas evaporated to dryness under reduced pressure.

In a second step, a poly(diallyl methyl amine) (PDMA) was synthesized. A50% aqueous solution of the monomer diallyl methyl ammoniumhydrochloride with 3.2% initiator of 2,2′-azobis(2-methylpropionamidine)dihydrochloride (AAPH) was purged with nitrogen for 20 minutes (min).Afterwards, the reaction was stirred under nitrogen atmosphere at 50° C.for 3 hours, and then the reaction was increased to 60° C. for another 6hours. The product poly(diallyl methyl ammonium hydrochloride) (PDMAH)was purified by dialysis and the water was removed on the rotaryevaporator under reduced pressure. Then, the PDMAH (1 part equivalentwith respect to monomer unit) was dissolved in a minimum amount ofmethanol and placed in an ice bath. Subsequently, sodium methoxide (1part equivalent) dissolved in a minimum amount of methanol, was added.The reaction was stored in a freezer for 1 hour. The PDMA methanolsolution was obtained after removing the NaCl with centrifugation.

In a third step, 6-bromo-N,N,N-tripropylhexan-1-aminium bromide (BTPAB)was synthesized. A tripropyl amine (0.05 mol)/toluene mixture (1:1volume/volume (v/v)) was added to 1,6-dibromohexane (0.1mol)/acetonitrile (1:1 v/v) slowly at 60° C. under magnetic stirring,and kept at this temperature for 24 hours. After cooling to roomtemperature and solvent evaporation, the obtained BTPAB was extractedthrough a diethyl ether-water system that separates excess 1,6-dibromohexane from the mixture.

In a fourth step, PDAMAB-TPHAB was synthesized. For the synthesis ofPDAMAB-TPHAB, 1 part equivalent of PDMA (with respect to monomer unit)in methanol was dissolved with 1 part equivalent of BTPAB inacetonitrile/toluene (40 mL, v:v=1:1) and refluxed at 70° C. for 72hours under magnetic stirring. After cooling to room temperature andthen solvent evaporation, the obtained PDAMAB-TPHAB was further purifiedby dialysis method in water.

The PDAMAB-TPHAB polymer synthesized in Example 1 was analyzed by¹H-MAS-NMR. The ¹H-MAS-NMR spectrum for the polymer produced in Example1 is depicted in FIG. 2 . The ¹H-MAS-NMR spectrum shows peaks at or near0.85 parts per million (ppm), at or near 1.3 ppm, at or near 1.6 ppm, ator near 2.8 ppm, and at or near 3.05 ppm.

Example 2—Synthesis of Mesoporous ZSM-5 Zeolite

A mesoporous ZSM-5 zeolite was formed having a Si/Al molar ratio of 30.In a typical synthesis, a homogeneous solution was prepared bydissolving 0.75 g of NaOH and 0.21 g of NaAlO₂ in 59.0 g of deionizedwater. This was followed by the addition 2.0 g ofpoly(N¹,N¹-diallyl-N¹-methyl-N⁶,N⁶,N⁶-tripropylhexane-1,6-diamoniumbromide), PDAMAB-TPHAB polymer under vigorous stirring at 60° C. Afterstirring for 1 hour, 16.5 g of tetraethyl orthosilicate (TEOS) was addeddropwise to the solution and further stirred for 12 hours at 60° C. Theobtained viscous gel was subjected to hydrothermal treatment at 150° C.for 60 hours. The resulting solids were washed, filtered and dried at110° C. for overnight. The as-synthesized solids were calcined at 550°C. for 6 hours at a heating rate of 1° C./min under static conditions.Then, an ion-exchange procedure was performed using 1.0 M NH₄NO₃solution at 80° C. The ion-exchanging process was repeated thrice priorto calcination at 550° C. for 4 hours in air to generate the H-form ofZSM-5 zeolite.

The mesoporous ZSM-5 zeolite of Example 2 was analyzed by powder X-raydiffraction (PXRD). The PXRD pattern of the mesoporous ZSM-5 zeolite ofExample 2 is displayed in FIG. 3 . Additionally, SEM images of themesoporous ZSM-5 zeolite of Example 2 were obtained and are displayed inFIGS. 4A and 4B. The SEM images displayed in FIGS. 4A and 4B show thatthe mesoporous ZSM-5 zeolite exhibits a nanofibrous morphology withparticle sizes ranging from about 200 to about 400 nm. The mesoporousZSM-5 zeolite of Example 2 was further analyzed by TEM imaging. TEMimages of the mesoporous ZSM-5 zeolite of Example 2 are displayed inFIGS. 5A-5K. These figures display uniform nanocrystals with MFIframeworks. The nanocrystals contain unidimensional nanorods that forminterconnected intercrystalline open-type mesopores. The TEM images showthat the lattice fringes originate from the MFI frameworks, whichindicates the crystalline nature of the mesoporous ZSM-5 zeolite ofExample 2.

Example 3—Synthesis of a Dehydroxylated ZSM-5 Zeolite at 700° C.

A dehydroxylated ZSM-5 zeolite was formed by treating 2 g of themesoporous ZSM-5 zeolite of Example 2 at a temperature of 700° C. and apressure of 10⁵ mbar for a time of 20 hours. Heating occurred at a rateof 150° C./hr. The dehydroxylated ZSM-5 zeolite of Example 3 wasanalyzed by Fourier transform infrared (FT-IR) spectroscopy. An FT-IRspectrum comparing the mesoporous ZSM-5 zeolite of Example 2 and thedehydroxylated ZSM-5 zeolite of Example 3 is displayed in FIG. 6 . Line810 (dashed line) refers to the FT-IR spectrum for the mesoporous ZSM-5zeolite of Example 2, and line 811 (solid line) refers to the FT-IRspectrum of dehydroxylated ZSM-5 zeolite of Example 3. The FT-IRspectrum of the dehydroxylated ZSM-5 zeolite of Example 3 in FIG. 6displays a peak at 3749 cm⁻¹ relating to isolated silanols and a peak at3613 cm⁻¹ relating to a Bronsted acid. These peaks are not present onthe FT-IR spectrum of the mesoporous ZSM-5 zeolite of Example 2, showingthat the dehydroxylation process described in Example 3 was successful.

The dehydroxylated ZSM-5 zeolite of Example 3 was analyzed by nuclearmagnetic resonance spectroscopy. A ¹H-MAS-NMR spectrum of thedehydroxylated ZSM-5 zeolite of Example 3 is displayed in FIG. 7 . The¹H-MAS-NMR spectrum of the dehydroxylated ZSM-5 zeolite of Example 3displays peaks at 2.77 ppm, 2.12 ppm, and 1.93 ppm. An Aluminum SolidState Nuclear Magnetic Resonance (²⁷Al—SS-NMR) spectrum of thedehydroxylated ZSM-5 zeolite of Example 3 is displayed in FIG. 8 . The27Al—SS-NMR spectrum of the dehydroxylated ZSM-5 zeolite of Example 3displays peaks at 54.69 ppm, 29.62 ppm, and 1.54 ppm.

Example 4—Synthesis of a Hafnium Modified ZSM-5 Zeolite

The dehydroxylated ZSM-5 of Example 3 was treated with theorganometallic chemical tetrakis(neopentyl)hafnium by the presentlydescribed method. 0.250 g of the dehydroxylated ZSM-5 of Example 3 and112 mg (0.24 mmol) of tetrakis(neopentyl)hafnium in 10 mL of dry anddegassed n-pentane were added to a double Schlenk tube and were stirredat room temperature for 6 hours. Afterwards, the resulting solids werewashed with 10 mL of dry and degassed n-pentane. This washing step wasrepeated twice more, resulting in a total of three washes using 10 mL ofdry and degassed n-pentane each. The solids were dried under a dynamicvacuum of less than 10⁻⁵ Torr at 90° C. for 12 hours to remove then-pentane from the resulting solids. The resulting solids were a ZSM-5zeolite modified with the hafnium organometallic chemicaltetrakis(neopentyl)hafnium, referred to herein as hafnium modified ZSM-5zeolite.

The hafnium modified ZSM-5 zeolite of Example 4 was analyzed by FT-IRspectroscopy. The FT-IR spectrum of the dehydroxylated ZSM-5 zeolite ofExample 3 and the FT-IR spectrum of the hafnium modified ZSM-5 zeoliteof Example 4 are displayed in FIG. 9 . Line 920 corresponds to the FT-IRspectrum of the dehydroxylated ZSM-5 zeolite of Example 3 and line 921corresponds to the FT-IR spectrum of the hafnium modified ZSM-5 zeoliteof Example 4. A decrease in the Si—OH peak at 3750 cm⁻¹ is exhibited inthe FT-IR spectrum of the hafnium modified ZSM-5 zeolite of Example 4.Additionally, peaks corresponding to neopentyl moieties appear at 2947cm⁻¹, 2865 cm⁻¹, 1468 cm⁻¹, and 1361 cm⁻¹. These peaks indicate that thedehydroxylated ZSM-5 zeolite of Example 3 was successfully modified withtetrakis(neopentyl)hafnium.

Having described the subject matter of the present disclosure in detailand by reference to specific embodiments, it is noted that the variousdetails described in this disclosure should not be taken to imply thatthese details relate to elements that are essential components of thevarious embodiments described in this disclosure, even in cases where aparticular element is illustrated in each of the drawings that accompanythe present description. Rather, the claims appended hereto should betaken as the sole representation of the breadth of the presentdisclosure and the corresponding scope of the various embodimentsdescribed in this disclosure. Further, it will be apparent thatmodifications and variations are possible without departing from thescope of the appended claims.

For the purposes of describing and defining the present disclosure it isnoted that the term “about” is utilized in this disclosure to representthe inherent degree of uncertainty that may be attributed to anyquantitative comparison, value, measurement, or other representation.The term “about” is also utilized in this disclosure to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue. Additionally, the term “consisting essentiallyof is used in this disclosure to refer to quantitative values that donot materially affect the basic and novel characteristic(s) of thedisclosure. For example, a chemical stream “consisting essentially” of aparticular chemical constituent or group of chemical constituents shouldbe understood to mean that the stream includes at least about 99.5% ofthat particular chemical constituent or group of chemical constituents.

It should be understood that any two quantitative values assigned to aproperty may constitute a range of that property, and all combinationsof ranges formed from all stated quantitative values of a given propertyare contemplated in this disclosure.

In a first aspect of the present disclosure, a modified zeolite maycomprise a microporous framework comprising a plurality of microporeshaving diameters of less than or equal to 2 nm. The microporousframework may comprise at least silicon atoms and oxygen atoms. Themodified zeolite may further comprise organometallic moieties eachbonded to bridging oxygen atoms. The organometallic moieties maycomprise a hafnium atom. The hafnium atom may be bonded to a bridgingoxygen atom, and bridging oxygen atom may bridge the hafnium atom of theorganometallic moiety and a silicon atom of the microporous framework.

A second aspect of the present disclosure may include the first aspectwhere the modified zeolite may further comprise a plurality of mesoporeshaving diameters of greater than 2 nm and less than or equal to 50 nm.

A third aspect of the present disclosure may include either of the firstor second aspects where the average pore size of the modified zeolitemay be greater than 2 nm.

A fourth aspect of the present disclosure may include any of the firstthrough third aspects where the mesoporous zeolite may compriseparticles of from 25 nm to 900 nm in size.

A fifth aspect of the present disclosure may include any of the firstthrough fourth aspects where the modified zeolite may be a ZSM-5zeolite.

A sixth aspect of the present disclosure may include any of the firstthrough fifth aspects where the microporous framework may furthercomprise aluminum atoms.

A seventh aspect of the present disclosure may include any of the firstthrough sixth aspects where the organometallic moieties may compriseHfR₁R₂R₃ and R₁ is chosen from any of an alkyl group, a hydride group, ahydroxyl group, an alkoxy group, an allyl group, a cyclopentadienylgroup, an amino group, an amido group, an imido group, a nitrido group,a carbene group, a carbyne group, a halogen group, a benzyl group, aphenyl group, or an oxide group; R₂ is chosen from any of an alkylgroup, a hydride group, a hydroxyl group, an alkoxy group, an allylgroup, a cyclopentadienyl group, an amino group, an amido group, animido group, a nitrido group, a carbene group, a carbyne group, a halidegroup, a benzyl group, a phenyl group, or an oxide group; and R₃ ischosen from any of an alkyl group, a hydride group, a hydroxyl group, analkoxy group, an allyl group, a cyclopentadienyl group, an amino group,an amido group, an imido group, a nitrido group, a carbene group, acarbyne group, a halide group, a benzyl group, a phenyl group, or anoxide group.

An eighth aspect of the present disclosure may include any of the firstthrough seventh aspects where the organometallic moieties may compriseHfR₁R₂R₃, where R₁ is an alkyl group; R₂ is an alkyl group; and R₃ is analkyl group.

A ninth aspect of the present disclosure may include any of the firstthrough eighth aspects where the organometallic moieties may comprisetris(neopentyl)hafnium.

In a tenth aspect of the present disclosure, a modified zeolite may bemade by a method comprising reacting an organometallic chemical with adehydroxylated zeolite. The dehydroxylated zeolite may comprise amicroporous framework comprising a plurality of micropores havingdiameters of less than or equal to 2 nm. The microporous framework maycomprise at least silicon atoms and oxygen atoms. The dehydroxylatedzeolite may comprise terminal isolated silanol functionalitiescomprising hydroxyl groups bonded to silicon atoms of the microporousframework. The reacting of the organometallic chemical with thedehydroxylated zeolite may form the modified zeolite includingorganometallic moieties each bonded to an oxygen atom of the modifiedzeolite. The organometallic moiety may comprise a portion of theorganometallic chemical, and the organometallic chemical may comprisehafnium.

An eleventh aspect of the present disclosure may include the tenthaspect where the modified zeolite may comprise a plurality of mesoporeshaving diameters of greater than 2 nm and less than or equal to 50 nm.

A twelfth aspect of the present disclosure may include either of thetenth or eleventh aspects where the average pore size of the modifiedzeolite may be greater than 2 nm.

A thirteenth aspect of the present disclosure may include any of thetenth through twelfth aspects where the method may further comprisedehydroxylating an initial zeolite to form the dehydroxylated zeolite,where the initial zeolite may primarily comprise vicinal silanolfunctionalities, and wherein dehydroxylating the initial zeolite mayform the terminal isolated silanol functionalities.

A fourteenth aspect of the present disclosure may include the thirteenthaspect where one or more of dehydroxylating the initial zeolite maycomprise heating the initial zeolite at a temperature of 650° C. to1100° C.; and dehydroxylating the initial zeolite may be under reducedpressure.

A fifteenth aspect of the present disclosure may include any of thetenth through fourteenth aspects where the microporous framework mayfurther comprise aluminum atoms.

A sixteenth aspect of the present disclosure may include any of thetenth through fifteenth aspects where the average pore size of thedehydroxylated zeolite may be greater than the size of theorganometallic chemical.

A seventeenth aspect of the present disclosure may include any of thetenth through sixteenth aspects where the organometallic chemical maycomprise HfR₁R₂R₃R₄, and R₁ is chosen from any of an alkyl group, ahydride group, a hydroxyl group, an alkoxy group, an allyl group, acyclopentadienyl group, an amino group, an amido group, an imido group,a nitrido group, a carbene group, a carbyne group, a halide group, abenzyl group, a phenyl group, or an oxide group; R₂ is chosen from anyof an alkyl group, a hydride group, a hydroxyl group, an alkoxy group,an allyl group, a cyclopentadienyl group, an amino group, an amidogroup, an imido group, a nitrido group, a carbene group, a carbynegroup, a halide group, a benzyl group, a phenyl group, or an oxidegroup; R₃ is chosen from any of an alkyl group, a hydride group, ahydroxyl group, an alkoxy group, an allyl group, a cyclopentadienylgroup, an amino group, an amido group, an imido group, a nitrido group,a carbene group, a carbyne group, a halide group, a benzyl group, aphenyl group, or an oxide group; and R₄ is chosen from any of an alkylgroup, a hydride group, a hydroxyl group, an alkoxy group, an allylgroup, a cyclopentadienyl group, an amino group, an amido group, animido group, a nitrido group, a carbene group, a carbyne group, a halidegroup, a benzyl group, a phenyl group, or an oxide group.

An eighteenth aspect of the present disclosure may include any of thetenth through seventeenth aspects where the organometallic chemical maycomprise HfR₁R₂R₃R₄, and R₁ is an alkyl group; R₂ is an alkyl group; R₃is an alkyl group; and R₄ is an alkyl group.

A nineteenth aspect of the present disclosure may include any of thetenth through eighteenth aspects where the organometallic chemical maycomprise tetrakis(neopentyl)hafnium.

A twentieth aspect of the present disclosure may include any of thetenth through nineteenth aspects where the organometallic moieties ofthe modified zeolite may comprise hafnium.

The invention claimed is:
 1. A modified zeolite comprising: amicroporous framework comprising a plurality of micropores havingdiameters of less than or equal to 2 nm, wherein the microporousframework comprises at least silicon atoms and oxygen atoms; andorganometallic moieties each bonded to bridging oxygen atoms, whereinthe organometallic moieties comprise a hafnium atom, wherein the hafniumatom is bonded to a bridging oxygen atom, wherein a concentration of theorganometallic moieties in the modified zeolite is at least 0.45 mmol/g,and wherein the bridging oxygen atom bridges the hafnium atom of theorganometallic moiety and a silicon atom of the microporous framework.2. The modified zeolite of claim 1, further comprising a plurality ofmesopores having diameters of greater than 2 nm and less than or equalto 50 nm.
 3. The modified zeolite of claim 1, wherein the average poresize of the modified zeolite is greater than 2 nm.
 4. The modifiedzeolite of claim 1, wherein the modified zeolite comprises particles offrom 25 nm to 900 nm in size.
 5. The modified zeolite of claim 1,wherein the modified zeolite is a ZSM-5 zeolite.
 6. The modified zeoliteof claim 1, wherein the microporous framework further comprises aluminumatoms.
 7. The modified zeolite of claim 1, wherein the organometallicmoieties comprise HfR₁R₂R₃, wherein: R₁ is chosen from any of an alkylgroup, a hydride group, a hydroxyl group, an alkoxy group, an allylgroup, a cyclopentadienyl group, an amino group, an amido group, animido group, a nitrido group, a carbene group, a carbyne group, ahalogen group, a benzyl group, a phenyl group, or an oxide group; R₂ ischosen from any of an alkyl group, a hydride group, a hydroxyl group, analkoxy group, an allyl group, a cyclopentadienyl group, an amino group,an amido group, an imido group, a nitrido group, a carbene group, acarbyne group, a halide group, a benzyl group, a phenyl group, or anoxide group; and R₃ is chosen from any of an alkyl group, a hydridegroup, a hydroxyl group, an alkoxy group, an allyl group, acyclopentadienyl group, an amino group, an amido group, an imido group,a nitrido group, a carbene group, a carbyne group, a halide group, abenzyl group, a phenyl group, or an oxide group.
 8. The modified zeoliteof claim 1, wherein the organometallic moieties comprise HfR₁R₂R₃,wherein: R₁ is an alkyl group; R₂ is an alkyl group; and R₃ is an alkylgroup.
 9. The modified zeolite of claim 1, wherein the organometallicmoieties comprise tris(neopentyl)hafnium.
 10. A method for making amodified zeolite, the method comprising: reacting an organometallicchemical with a dehydroxylated zeolite, wherein the dehydroxylatedzeolite comprises a microporous framework comprising a plurality ofmicropores having diameters of less than or equal to 2 nm, wherein themicroporous framework comprises at least silicon atoms and oxygen atoms,and wherein the dehydroxylated zeolite comprises isolated terminalsilanol functionalities comprising hydroxyl groups bonded to siliconatoms of the microporous framework; wherein the reacting of theorganometallic chemical with the dehydroxylated zeolite forms themodified zeolite comprising the microporous framework comprising aplurality of micropores having diameters of less than or equal to 2 nm,wherein the microporous framework comprises at least silicon atoms andoxygen atoms, and organometallic moieties each bonded to bridging oxygenatoms, wherein the organometallic moieties comprise a hafnium atom,wherein the titanium atom is bonded to a bridging oxygen atom, wherein aconcentration of the organometallic moieties in the modified zeolite isat least 0.45 mmol/g, and wherein the bridging oxygen atom bridges thehafnium atom of the organometallic moiety and a silicon atom of themicroporous framework, wherein the organometallic moiety comprises aportion of the organometallic chemical; and wherein the organometallicchemical comprises hafnium.
 11. The method of claim 10, wherein themodified zeolite comprises a plurality of mesopores having diameters ofgreater than 2 nm and less than or equal to 50 nm.
 12. The method ofclaim 10, wherein the average pore size of the modified zeolite isgreater than 2 nm.
 13. The method of claim 10, further comprisingdehydroxylating an initial zeolite to form the dehydroxylated zeolite,wherein the initial zeolite primarily comprises vicinal silanolfunctionalities, and wherein dehydroxylating the initial zeolite formsthe isolated terminal silanol functionalities.
 14. The method of claim13, wherein one or more of: dehydroxylating the initial zeolitecomprises heating the initial zeolite at a temperature of 650° C. to1100° C.; and dehydroxylating the initial zeolite is under reducedpressure.
 15. The method of claim 10, wherein the microporous frameworkfurther comprises aluminum atoms.
 16. The method of claim 10, whereinthe average pore size of the dehydroxylated zeolite is greater than thesize of the organometallic chemical.
 17. The method of claim 10, whereinthe organometallic chemical comprises HfR₁R₂R₃R₄, wherein: R₁ is chosenfrom any of an alkyl group, a hydride group, a hydroxyl group, an alkoxygroup, an allyl group, a cyclopentadienyl group, an amino group, anamido group, an imido group, a nitrido group, a carbene group, a carbynegroup, a halide group, a benzyl group, a phenyl group, or an oxidegroup; R₂ is chosen from any of an alkyl group, a hydride group, ahydroxyl group, an alkoxy group, an allyl group, a cyclopentadienylgroup, an amino group, an amido group, an imido group, a nitrido group,a carbene group, a carbyne group, a halide group, a benzyl group, aphenyl group, or an oxide group; R₃ is chosen from any of an alkylgroup, a hydride group, a hydroxyl group, an alkoxy group, an allylgroup, a cyclopentadienyl group, an amino group, an amido group, animido group, a nitrido group, a carbene group, a carbyne group, a halidegroup, a benzyl group, a phenyl group, or an oxide group; and R₄ ischosen from any of an alkyl group, a hydride group, a hydroxyl group, analkoxy group, an allyl group, a cyclopentadienyl group, an amino group,an amido group, an imido group, a nitrido group, a carbene group, acarbyne group, a halide group, a benzyl group, a phenyl group, or anoxide group.
 18. The method of claim 10, wherein the organometallicchemical comprises HfR₁R₂R₃R₄, wherein: R₁ is an alkyl group; R₂ is analkyl group; R₃ is an alkyl group; and R₄ is an alkyl group.
 19. Themethod of claim 10, wherein the organometallic chemical comprisestetrakis(neopentyl)hafnium.
 20. The method of claim 10, wherein theorganometallic moieties of the modified zeolite comprise hafnium.